Field of the Invention
The present invention relates to a wireless communication apparatus including a blocking member configured to block an electromagnetic wave radiated from an antenna, and an electronic apparatus including a wireless communication apparatus.
Description of the Related Art
In recent years, a wireless communication apparatus having a wireless communication function has been mounted to an electronic apparatus that is an image pickup apparatus (e.g., a digital camera), which enables the image pickup apparatus to wirelessly transmit a signal of a picked-up image to another camera or a PC (Personal Computer) by a wireless LAN (Local Area Network), Bluetooth (trademark), or the like. In wireless communication by a wireless LAN, Bluetooth (trademark), or the like, a radio wave of a 2.4 [GHz] band or a 5 [GHz] band is used. A wireless communication apparatus is built into an electronic apparatus in some cases. In other cases, a wireless communication apparatus is mounted to, for example, a digital single-lens reflex camera that is an image pickup apparatus as an external option. Mounting this option to a camera enables, for example, wireless communication to/from a communication partner separated from the camera by 100 meters or more.
In this type of wireless communication apparatus, when a high-power electromagnetic wave radiated from an antenna intrudes into a human body and its energy is absorbed into the human body, there is a concern of a local temperature increase in the human body. There has been pointed out a possibility of, for example, an increased risk of developing cataract due to this local temperature increase in the human body. For this reason, in each country, a regulatory value of an absorption amount of the electromagnetic wave into a human body is defined as a specific absorption ratio (SAR) value.
As a technology for suppressing the SAR value below its regulatory value, as disclosed in Japanese Patent Application Laid-Open No. 2005-45646, there has been proposed a configuration in which a metal plate having larger external dimensions than those of an antenna is arranged between a human body and the antenna so that a propagation direction of a radio wave is limited to the one opposite to the human body.
However, with the configuration of Japanese Patent Application Laid-Open No. 2005-45646, although the SAR value is decreased through the arrangement of the metal plate, there is a problem in that radiation efficiency of the electromagnetic wave at a communication frequency is decreased due to resonance between the metal plate and the antenna.
Moreover, as a result of measurement of directivity of the electromagnetic wave in the antenna using the configuration in which the entire antenna is shielded with the metal plate as disclosed in Japanese Patent Application Laid-Open No. 2005-45646, an amount of radio waves radiated in the direction toward the metal plate (direction toward the human body) was decreased through the arrangement of the metal plate. Even under a state in which the amount of radio waves radiated toward the metal plate side is thus decreased, communication can be established when communication partners exist in various directions from the antenna as in the case of a base station of mobile phones. However, under a situation in which one-to-one communication is performed between, for example, a camera and a PC, when a communication partner exists in the direction of the metal plate, there is a problem in that a communicable distance or an effective data transfer rate is significantly decreased due to a bias of the directivity of the electromagnetic wave in the antenna.